Sifter

Abstract

The invention relates to a sifter having a dispersing plate which has material passage openings therein. The dispersing plate carries guide elements and distributor elements adjacent such openings which are inclined with respect to the radius of the plate. Such a dispersing plate makes it possible to feed the material to be sifted into the sifting chamber very evenly.

What is claimed is: 
     
       1. In a sifter comprising: (a) a rotor rotatable about a vertical axis and having blades circumferentially spaced about its periphery for guiding a stream of sifting air;   (b) an annular dispersing plate rotatable with the rotor and positioned on its upper face;   (c) means for delivering material to be sifted to the dispersing plate;   (d) a distributor encircling the rotor and having guide vanes for delivering a stream of sifting air through the distributor and the rotor inwardly thereof;   (e) means above the rotor for discharging the stream of sifting air and relatively fine material entrained therein; and   (f) means below the rotor and the distributor for removal of relatively coarse material,   the improvement wherein:   (g) the dispersing plate has in its peripheral zone a plurality of openings distributed substantially evenly over the periphery, the openings are arranged so as to have radially outer and inner ends;   (h) guide elements are positioned adjacent the radially outer ends of said openings, said guide elements being positioned so as to form an angle with respect to the radius of said plate and in the direction of rotation of said plate; and   (i) distributor elements are positioned between the radially outer ends of the individual guide elements and the radially inner ends of the leading guide elements in the direction of rotation, said distributor elements being positioned so as to form an angle with respect to the radius of said plate and against the direction of rotation of said plate.   
     
     
       2. A sifter according to claim 1, wherein the angle which the guide elements form with the radius of said plate is between 34° and 54°. 
     
     
       3. A sifter according to claim 2 wherein said angle is about 45°. 
     
     
       4. A sifter according to claim 1 wherein the angle which the distributor elements form with the radius of said plate is between 25° and 45°. 
     
     
       5. A sifter according to claim 4 wherein said angle is about 36°. 
     
     
       6. A sifter according to claim 1 wherein said openings are arranged on a diameter which corresponds substantially to the average diameter of said distributor. 
     
     
       7. A sifter according to claim 1 wherein the guide elements are inclined with respect to the vertical and at least partially cover the openings with a clearance. 
     
     
       8. A sifter according to claim 1 wherein the openings extend into wedge-shaped zones between adjoining guide elements and distributor elements which are arranged in zigzag formation. 
     
     
       9. A sifter according to claim 1 wherein the openings are constructed as slots the axes of which are substantially parallel to the axes of the guide elements. 
     
     
       10. A sifter according to claim 1 wherein the openings have four corners. 
     
     
       11. A sifter according to claim 10 wherein the openings are trapeziform in shape, with the base of the trapezium defined by the guide elements. 
     
     
       12. A sifter according to claim 1 wherein the means for delivering material to be sifted contains a plurality of diametrally arranged material delivery tubes. 
     
     
       13. A sifter according to claim 1 including a radial space between the rotor and the distribution and wherein said guide vanes are adjustable about a vertical axis that is eccentric whereby the radial space between the guide vanes and the rotor remains constant regardless of the position of the guide vanes.